Relaying broadcast messages to out-of-coverage user equipment

Abstract

Methods, systems, and devices for wireless communications are described. Aspects of the present disclosure relate to an in-coverage user equipment (UE) relaying broadcast messages to out-of-coverage UEs using one or more messaging techniques over a sidelink channel. The in-coverage UE may monitor for broadcast messages to relay the broadcast messages to out-of-coverage UEs. In some cases, the in-coverage UE may determine to relay broadcast messages to the out-of-coverage UEs based on one or more metrics. Additionally, the in-coverage UE may determine whether the broadcast message is to be included in a groupcast, broadcast, or unicast signaling. Based on the determination to relay broadcast messages, as well as whether the alert message is to be included in a groupcast, broadcast, or unicast signaling, the in-coverage UE may leverage sidelink communications to relay broadcast messages to the out-of-coverage UEs.

What is claimed is: 
     
       1. A method of wireless communications at a first user equipment (UE), comprising:
 receiving a broadcast message from a network entity; 
 receiving a configuration based at least in part on a first parameter indicating a location associated with the first UE, a power parameter associated with the first UE, or both; and 
 relaying, according to the configuration for relaying broadcast messages from the network entity to at least a second UE that is determined to be out of coverage of the network entity, the received broadcast message over a sidelink channel to at least the second UE. 
 
     
     
       2. The method of  claim 1 , wherein relaying the broadcast message comprises:
 transmitting, to at least the second UE, signaling comprising a groupcast message, a broadcast message, or both. 
 
     
     
       3. The method of  claim 2 , wherein the signaling comprises a medium access control-control element (MAC-CE) and the sidelink channel comprises a physical sidelink shared channel (PSSCH). 
     
     
       4. The method of  claim 3 , wherein the MAC-CE is multiplexed with other signaling over the PSSCH based at least in part on a configurable priority threshold. 
     
     
       5. The method of  claim 2 , wherein the signaling comprises a physical sidelink control channel (PSCCH) carrying sidelink control information (SCI) and a PSSCH message. 
     
     
       6. The method of  claim 5 , wherein the SCI indicates that the PSSCH message comprises a relayed broadcast message. 
     
     
       7. The method of  claim 1 , wherein relaying the broadcast message comprises:
 transmitting, to at least the second UE, signaling comprising a unicast message. 
 
     
     
       8. The method of  claim 7 , wherein the signaling comprises a PC5 radio resource control (RRC) message over the sidelink channel and the sidelink channel comprises a physical sidelink control channel (PSCCH) and a physical sidelink shared channel (PSSCH). 
     
     
       9. The method of  claim 1 , wherein the broadcast message comprises an alert message. 
     
     
       10. The method of  claim 1 , wherein the broadcast message is indicated in a system information block (SIB) or a master information block (MIB). 
     
     
       11. The method of  claim 1 , wherein the configuration for relaying broadcast messages from the network entity to at least the second UE is statically configured or semi-statically configured via radio resource control (RRC) signaling. 
     
     
       12. The method of  claim 1 , further comprising:
 receiving downlink control information (DCI) over a physical downlink control channel (PDCCH) that dynamically enables or disables for a duration relaying of broadcast messages from the network entity to at least the second UE. 
 
     
     
       13. The method of  claim 1 , further comprising:
 receiving control signaling indicating the configuration. 
 
     
     
       14. The method of  claim 1 , wherein the configuration is preconfigured at the first UE. 
     
     
       15. The method of  claim 1 , further comprising:
 receiving second control signaling indicating a modification to the configuration for relaying broadcast messages. 
 
     
     
       16. The method of  claim 15 , wherein the second control signaling comprises a second medium access control-control element (MAC-CE) over a physical sidelink shared channel (PSSCH). 
     
     
       17. The method of  claim 15 , wherein the second control signaling comprises a second PC5 radio resource control (RRC) message over a physical sidelink control channel (PSCCH) or a physical sidelink shared channel (PSSCH). 
     
     
       18. A method for wireless communications at a second user equipment (UE), comprising:
 receiving a configuration for receiving relayed broadcast messages from a first UE, wherein the broadcast messages are relayed from the first UE to the second UE, wherein the first UE is in coverage of a network entity and wherein the second UE is determined to be out of coverage of the network entity, wherein the configuration includes signaling comprising a medium access control-control element (MAC-CE); and 
 receiving a relay message over a sidelink channel from the first UE according to the configuration, wherein the sidelink channel comprises a physical sidelink shared channel (PSSCH), wherein the MAC-CE is multiplexed with other signaling over the PSSCH based at least in part on a configurable priority threshold. 
 
     
     
       19. The method of  claim 18 , wherein the broadcast messages comprise
 a groupcast message, a broadcast message, or both. 
 
     
     
       20. The method of  claim 18 , wherein the broadcast messages comprise
 a unicast message. 
 
     
     
       21. The method of  claim 18 , wherein the signaling comprises a PC5 radio resource control (RRC) message over the sidelink channel and the sidelink channel comprises a physical sidelink control channel (PSCCH) and a physical sidelink shared channel (PSSCH). 
     
     
       22. The method of  claim 18 , wherein the broadcast messages comprise an alert message. 
     
     
       23. The method of  claim 18 , wherein the broadcast messages are indicated in a system information block (SIB) or a master information block (MIB). 
     
     
       24. An apparatus, comprising:
 a processor; 
 memory coupled with the processor; and 
 instructions stored in the memory and executable by the processor to cause the apparatus to: 
 receive a broadcast message from a network entity; 
 receive a configuration message based at least in part on a first parameter indicating a location associated with the first UE, a power parameter associated with the first UE, or both; and 
 relay, according to the configuration for relaying broadcast messages from the network entity to at least a second UE that is determined to be out of coverage of the network entity, the received broadcast message over a sidelink channel to at least the second UE. 
 
     
     
       25. The apparatus of  claim 24 , wherein the instructions to relay the broadcast message are executable by the processor to cause the apparatus to:
 transmit, to at least the second UE, signaling comprising a groupcast message, a broadcast message, or both. 
 
     
     
       26. The apparatus of  claim 25 , wherein the signaling comprises a medium access control-control element (MAC-CE) and the sidelink channel comprises a physical sidelink shared channel (PSSCH). 
     
     
       27. An apparatus for wireless communications at a second user equipment (UE), comprising:
 a processor; 
 memory coupled with the processor; and 
 instructions stored in the memory and executable by the processor to cause the apparatus to: 
 receive a configuration for receiving relayed broadcast messages from a first UE, wherein the broadcast messages are relayed from the first UE to the second UE, wherein the first UE is in coverage of a network entity and wherein the second UE is determined to be out of coverage of the network entity, wherein the configuration includes signaling comprising a medium access control-control element (MAC-CE); and 
 receive a relay message over a sidelink channel from the first UE according to the configuration, wherein the sidelink channel comprises a physical sidelink shared channel (PSSCH), wherein the MAC-CE is multiplexed with other signaling over the PSSCH based at least in part on a configurable priority threshold.